Transcript Chapter 3

Chapter 3
The Molecules of Life
Laura Coronado
Bio 10
Chapter 3
Biology and Society: Got Lactose?
– Lactose is the main sugar found in milk.
– Some adults exhibit lactose intolerance, the inability to
properly digest lactose.
– Lactose-intolerant individuals are unable to digest
lactose properly.
• Lactose is broken down by bacteria in the large
intestine producing gas and discomfort.
– There is no treatment for the underlying cause of
lactose intolerance.
– Affected people must avoid lactose-containing foods or
take the enzyme lactase when eating dairy products
Laura Coronado
Bio 10
Chapter 3
Laura Coronado
Bio 10
Chapter 3
Figure 3.00
ORGANIC COMPOUNDS
– A cell is mostly water.
– The rest of the cell consists mainly of
carbon-based molecules.
– Carbon forms large, complex, and diverse
molecules necessary for life’s functions.
– Organic compounds are carbon-based
molecules.
Laura Coronado
Bio 10
Chapter 3
Carbon Chemistry
– Carbon is a versatile atom.
• It has four electrons in an outer shell that holds
eight.
• Carbon can share its electrons with other atoms to
form up to four covalent bonds.
– Carbon can use its bonds to
• Attach to other carbons
• Form an endless diversity of carbon skeletons
Animation: Carbon Skeletons
Laura Coronado
Bio 10
Chapter 3
Double bond
Carbon skeletons may have double bonds,
which can vary in location
Carbon skeletons vary in length
Carbon skeletons may be unbranched or branched
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Carbon skeletons may be arranged in rings
Bio 10
Chapter 3
Figure 3.1
Hydrocarbons
– The simplest organic compounds are
hydrocarbons, which are organic molecules
containing only carbon and hydrogen
atoms.
– The simplest hydrocarbon is methane,
consisting of a single carbon atom bonded
to four hydrogen atoms.
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Bio 10
Chapter 3
Structural formula
Ball-and-stick model
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Bio 10
Space-filling model
Chapter 3
Figure 3.2
Laura Coronado
Bio 10
Chapter 3
Figure 3.3
Organic Molecule
– Each type of organic molecule has a unique threedimensional shape.
– The shapes of organic molecules relate to their
functions.
– The unique properties of an organic compound depend
on
• Its carbon skeleton
• The atoms attached to the skeleton
– The groups of atoms that usually participate in chemical
reactions are called functional groups. Two common
examples are
• Hydroxyl groups (-OH)
• Carboxyl groups (C=O)
Laura Coronado
Bio 10
Chapter 3
Giant Molecules from Smaller
Building Blocks
– On a molecular scale, many of life’s
molecules are gigantic, earning the name
macromolecules.
– Three categories of macromolecules are
• Carbohydrates
• Proteins
• Nucleic acids
Laura Coronado
Bio 10
Chapter 3
Giant Molecules from Smaller
Building Blocks
– Most macromolecules are polymers.
– Polymers are made by stringing together
many smaller molecules called monomers.
– A dehydration reaction
• Links two monomers together
• Removes a molecule of water
Animation: Polymers
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Bio 10
Chapter 3
Short polymer
Monomer
Dehydration
reaction
Longer polymer
a Building a polymer chain
Laura Coronado
Bio 10
Chapter 3
Figure 3.4a
Hydrolysis Reaction
– Organisms also have to break down
macromolecules.
– Hydrolysis
• Breaks bonds between monomers
• Adds a molecule of water
• Reverses the dehydration reaction
Laura Coronado
Bio 10
Chapter 3
Hydrolysis
b Breaking a polymer chain
Laura Coronado
Bio 10
Chapter 3
Figure 3.4b
LARGE BIOLOGICAL MOLECULES
– There are four categories of large molecules
in cells:
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Laura Coronado
Bio 10
Chapter 3
Carbohydrates
– Carbohydrates are sugars or sugar
polymers. They include
• Small sugar molecules in soft drinks
• Long starch molecules in pasta and potatoes
Laura Coronado
Bio 10
Chapter 3
Monosaccharides
– Monosaccharides are simple sugars that cannot
be broken down by hydrolysis into smaller
sugars.
– Glucose and fructose are isomers, molecules
that have the same molecular formula but
different structures.
– Monosaccharides are the main fuels for cellular
work.
– In aqueous solutions, many monosaccharides
Animation: L-Dopa
form rings.
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Bio 10
Chapter 3
Glucose
Fructose
C6H12O6
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Bio 10
C6H12O6
Isomers
Figure 3.5
Chapter 3
Glucose
Fructose
C6H12O6
C6H12O6
Isomers
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Bio 10
Chapter 3
Figure 3.5a
b Abbreviated
ring structure
a Linear and ring structures
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Bio 10
Chapter 3
Figure 3.6
Disaccharides
– A disaccharide is
• A double sugar
• Constructed from two monosaccharides
• Formed by a dehydration reaction
– Disaccharides include
• Lactose in milk
• Maltose in beer, malted milk shakes, and malted
milk ball candy
• Sucrose in table sugar
Animation: Disaccharides
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Bio 10
Chapter 3
Galactose
Glucose
Lactose
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Bio 10
Chapter 3
Figure 3.7
Disaccharides
– Sucrose is
• The main carbohydrate in plant sap
• Rarely used as a sweetener in processed foods
– High-fructose corn syrup is made by a
commercial process that converts natural
glucose in corn syrup to much sweeter fructose.
– The United States is one of the world’s leading
markets for sweeteners.
• The average American consumes about 45 kg of
sugar (about 100 lbs.) per year.
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Bio 10
Chapter 3
processed to extract
Starch
broken down into
Glucose
converted to sweeter
Fructose
added to foods as
high-fructose corn syrup
Ingredients: carbonated water,
high-fructose corn syrup,
caramel color, phosphoric acid,
natural flavors
Laura Coronado
Bio 10
Chapter 3
Figure 3.8
Polysaccharides
– Polysaccharides are
• Complex carbohydrates
• Made of long chains of sugar units and polymers
of monosaccharides
– Starch is an example of a polysaccharide
• Used by plant cells to store energy
• Potatoes and grains are major sources of starch in
the human diet.
Animation: Polysaccharides
Laura Coronado
Bio 10
Chapter 3
Glucose
monomer
Starch granules
a Starch
Glycogen
granules
b Glycogen
Cellulose fibril
Cellulose
molecules
c Cellulose
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Bio 10
Chapter 3
Figure 3.9
Glycogen
– Glycogen is
• Used by animals cells to store energy
• Converted to glucose when it is needed
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Bio 10
Chapter 3
Cellulose
– Cellulose
• Is the most abundant organic compound on Earth
• Forms cable-like fibrils in the tough walls that
enclose plants
• Cannot be broken apart by most animals
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Bio 10
Chapter 3
Carbohydrates in Water
– Monosaccharides and disaccharides dissolve
readily in water.
– Cellulose does not dissolve readily in water.
– Almost all carbohydrates are hydrophilic, or
“water-loving,” adhering water to their
surface.
Laura Coronado
Bio 10
Chapter 3
Lipids & Fats
– Lipids are
• Neither macromolecules nor polymers
• Hydrophobic, unable to mix with water
• A typical fat, or triglyceride, consists of a glycerol
molecule joined with three fatty acid molecules via
a dehydration reaction.
• Essential functions in the human body including
• Energy storage
• Cushioning
• Insulation
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Bio 10
Chapter 3
Oil (hydrophobic)
Vinegar (hydrophilic)
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Bio 10
Chapter 3
Figure 3.10
Fatty acid
Glycerol
(a) A dehydration reaction linking a fatty acid to glycerol
(b) A fat molecule with a glycerol “head” and three
energy-rich hydrocarbon fatty acid “tails”
Laura Coronado
Bio 10
Chapter 3
Figure 3.11
Fatty Acid
– If the carbon skeleton of a fatty acid has
• Fewer than the maximum number of hydrogens, it
is unsaturated
• The maximum number of hydrogens, then it is
saturated
– A saturated fat has no double bonds, and all
three of its fatty acids are saturated.
Laura Coronado
Bio 10
Chapter 3
Lipids & Fats
– Most plant oils tend to be low in saturated
fatty acids and liquid at room temperature.
– Most animal fats
• Have a high proportion of saturated fatty acids
• Can easily stack, tending to be solid at room
temperature
• Contribute to atherosclerosis, a condition in
which lipid-containing plaques build up within
the walls of blood vessels
Laura Coronado
Bio 10
Chapter 3
Hydrogenation
– Hydrogenation
• Adds hydrogen
• Converts unsaturated fats to saturated fats
• Makes liquid fats solid at room temperature
• Creates trans fat, a type of unsaturated fat that is
even less healthy than saturated fats
Laura Coronado
Bio 10
Chapter 3
TYPES OF FATS
Saturated Fats
Unsaturated Fats
Margarine
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID
Trans fats
Plant oils
Laura Coronado
ANTIOXIDANTS
Bio 10
Chapter 3
Figure 3.12
Omega-3 fats
Unsaturated Fats
Margarine
INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED
COTTONSEED OIL, PARTIALLY HYDROGENATED
COTTONSEED OIL AND SOYBEAN OILS, MONO AND
DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS
Plant oils
Trans fats
Laura Coronado
Bio 10
Omega-3 fats
Chapter 3
Figure 3.12b
Steroids
– Steroids are very different from fats in
structure and function.
• The carbon skeleton is bent to form four fused
rings.
• Steroids vary in the functional groups attached to
this core set of rings.
– Cholesterol
• A key component of cell membranes
• The “base steroid” from which your body produces
other steroids, such as estrogen and testosterone
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Bio 10
Chapter 3
Cholesterol
Testosterone
A type of estrogen
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Bio 10
Chapter 3
Figure 3.13
Steroids
– Synthetic anabolic steroids
• Resemble testosterone
• Mimic some of its effects
• Can cause serious physical and mental problems
• Are abused by athletes to enhance performance
Laura Coronado
Bio 10
Chapter 3
THG
Laura Coronado
Bio 10
Chapter 3
Figure 3.14
Proteins
– Proteins
• Are polymers constructed from amino acid
monomers
• Perform most of the tasks the body needs to
function
• Form enzymes, chemicals that change the rate of a
chemical reaction without being changed in the
process
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Bio 10
Chapter 3
MAJOR TYPES OF PROTEINS
Structural Proteins
Storage Proteins
Contractile Proteins
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Bio 10
Transport Proteins
Chapter 3
Figure 3.15
Enzymes
The Monomers of Proteins: Amino
Acids
– All proteins are constructed from a common
set of 20 kinds of amino acids.
– Each amino acid consists of a central carbon
atom bonded to four covalent partners in
which three of those attachment groups are
common to all amino acids.
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Bio 10
Chapter 3
Amino
group
Carboxyl
group
Side
group
a The general structure of an amino acid
Hydrophobic
side group
Hydrophilic
side group
Leucine
Serine
b Examples of amino acids with hydrophobic and hydrophilic
side groups
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Bio 10
Chapter 3
Figure 3.16
Proteins as Polymers
– Cells link amino acids together by dehydration
reactions, forming peptide bonds and creating
long chains of amino acids called
polypeptides.
– Your body has tens of thousands of different
kinds of protein.
– Proteins differ in their arrangement of amino
acids.
– The specific sequence of amino acids in a
protein is its primary structure.
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Bio 10
Chapter 3
Carboxyl
group
Amino
group
Side
group
Side
group
Amino acid
Amino acid
Dehydration reaction
Side
group
Side
group
Peptide bond
Laura Coronado
Bio 10
Chapter 3
Figure 3.17-2
15
5
1
10
30
35
20
25
45
40
50
55
65
60
70
75
Amino acid
85
80
95
100
90
110
115
105
125
120
129
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Bio 10
Chapter 3
Figure 3.18
SEM
1
2
Normal red blood cell
3
4
5
6
7. . . 146
Normal hemoglobin
SEM
a Normal hemoglobin
1
Sickled red blood cell
b Sickle-cell hemoglobin Laura Coronado
2
3
4
5
6
Sickle-cell hemoglobin
Bio 10
Chapter 3
Figure 3.19
7. . . 146
Protein Shape
– A functional protein consists of one or more
polypeptide chains, precisely folded and coiled
into a molecule of unique shape.
– Proteins consisting of
• One polypeptide have three levels of structure
• More than one polypeptide chain have a fourth,
quaternary structure
– A protein’s three-dimensional shape
• Recognizes and binds to another molecule
• Enables the protein to carry out its specific function
in a cell
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Bio 10
Chapter 3
Amino
acids
b Secondary structure
c Tertiary
structure
d Quaternary
structure
a Primary
structure
Pleated sheet
Protein with
four polypeptides
Polypeptide
Alpha helix
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Bio 10
Chapter 3
Figure 3.20-4
Target
Protein
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Bio 10
Chapter 3
Figure 3.21
What Destroys Protein Shape?
– A protein’s shape is sensitive to the
surrounding environment.
– Unfavorable temperature and pH changes
can cause denaturation of a protein, in
which it unravels and loses its shape.
– High fevers (above 104º F) in humans can
cause some proteins to denature.
Laura Coronado
Bio 10
Chapter 3
Protein Structural Errors
– Misfolded proteins are associated with
• Alzheimer’s disease
• Mad cow disease
• Parkinson’s disease
Laura Coronado
Bio 10
Chapter 3
Genetic Information
– Nucleic acids are macromolecules that provide the
directions for building proteins
• Include DNA and RNA
• Are the genetic material that organisms inherit
from their parents
– DNA resides in cells in long fibers called
chromosomes.
– A gene is a specific stretch of DNA that programs
the amino acid sequence of a polypeptide.
– The chemical code of DNA must be translated from
“nucleic acid language” to “protein language.”
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Bio 10
Chapter 3
Gene
DNA
Nucleic acids
RNA
Amino acid
Protein
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Bio 10
Chapter 3
Figure 3.22
Nucleotides
– Nucleic acids are polymers of nucleotides.
– Each nucleotide has three parts:
•
•
•
A five-carbon sugar
A phosphate group
A nitrogenous base
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Bio 10
Chapter 3
Nitrogenous base
A, G, C, or T
Thymine T
Phosphate
group
Phosphate
Base
Sugar
deoxyribose
Sugar
a Atomic structure
b Symbol used in this book
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Bio 10
Chapter 3
Figure 3.23
DNA
– Each DNA nucleotide has one of the following
bases:
• Adenine (A)
• Guanine (G)
• Thymine (T)
• Cytosine (C)
Laura Coronado
Bio 10
Chapter 3
Adenine A
Guanine G
Thymine T
Adenine A
Cytosine C
Guanine G
Space-filling model of DNA
Laura Coronado
Thymine T
Bio 10
Cytosine C
Chapter 3
Figure 3.24
DNA Linkages
– Dehydration reactions
• Link nucleotide monomers into long chains called
polynucleotides
• Form covalent bonds between the sugar of one
nucleotide and the phosphate of the next
• Form a sugar-phosphate backbone
– Nitrogenous bases hang off the sugarphosphate backbone.
Laura Coronado
Bio 10
Chapter 3
Sugar-phosphate
backbone
Nucleotide
Base
pair
Hydrogen
bond
Bases
a DNA strand
polynucleotide
Laura Coronado
b Double helix
two
polynucleotide
strands
Bio 10
Chapter 3
Figure 3.25
DNA Linkages
– Two strands of DNA join together to form a
double helix.
– Bases along one DNA strand hydrogen-bond to
bases along the other strand.
– The functional groups hanging off the base
determine which bases pair up:
• A only pairs with T.
• G can only pair with C.
Laura Coronado
Bio 10
Chapter 3
RNA
– RNA, ribonucleic acid, is different from DNA.
• RNA is usually single-stranded but DNA usually
exists as a double helix.
• RNA uses the sugar ribose and the base uracil (U)
instead of thymine (T).
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Bio 10
Chapter 3
Nitrogenous base
A, G, C, or U
Uracil U
Phosphate
group
Sugar ribose
Laura Coronado
Bio 10
Chapter 3
Figure 3.26
The Process of Science:
Does Lactose Intolerance Have a
Genetic Basis?
– Observation: Most lactose-intolerant people
have a normal version of the lactase gene.
– Question: Is there a genetic basis for lactose
intolerance?
– Hypothesis: Lactose-intolerant people have a
mutation but not within the lactase gene.
Laura Coronado
Bio 10
Chapter 3
The Process of Science:
Does Lactose Intolerance Have a
Genetic Basis?
– Prediction: A mutation would be found nearby
the lactase gene.
– Experiment: Genes of 196 lactose-intolerant
people were examined.
– Results: A 100% correlation between lactose
intolerance and one mutation was found.
Laura Coronado
Bio 10
Chapter 3
DNA
Lactase gene
14,000 nucleotides
Human cell
DNA in 46
chromosomes
Chromosome 2
one DNA molecule
Laura Coronado
Bio 10
Section of
chromosome 2
Chapter 3
C at this site causes
lactose intolerance
T at this site causes
lactose tolerance
Figure 3.27
Evolution Connection:
Evolution and Lactose Intolerance in Humans
– Most people are lactose-intolerant as adults:
• African Americans and Native Americans — 80%
• Asian Americans — 90%
• But only 10% of Americans of northern European
descent are lactose-intolerant
Laura Coronado
Bio 10
Chapter 3
Lactose Tolerance
– Lactose tolerance appears to have evolved in
northern European cultures that relied upon
dairy products.
– Ethnic groups in East Africa that rely upon
dairy products are also lactose tolerant but
due to different mutations.
Laura Coronado
Bio 10
Chapter 3
Large biological
molecules
Carbohydrates
Functions
Components
Examples
Monosaccharides:
glucose, fructose
Disaccharides:
lactose, sucrose
Polysaccharides:
starch, cellulose
Dietary energy;
storage; plant
structure
Monosaccharide
Lipids
Long-term
energy storage
fats;
hormones
steroids
Fatty acid
Glycerol
Components of
a triglyceride
Amino
group
Proteins
Enzymes, structure,
storage, contraction,
transport, and others
Fats triglycerides;
Steroids
testosterone,
estrogen
Carboxyl
group
Side
group
Lactase
an enzyme,
hemoglobin
a transport protein
Amino acid
Phosphate
Base
Nucleic acids
Information
storage
DNA, RNA
Sugar
Laura Coronado
Nucleotide
Bio 10
Chapter 3
Figure UN3-2
Carbohydrates
Functions
Components
Examples
Monosaccharides:
glucose, fructose
Disaccharides:
lactose, sucrose
Polysaccharides:
starch, cellulose
Dietary energy;
storage; plant
structure
Monosaccharide
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2a
Lipids
Functions
Long-term
energy storage
fats;
hormones
steroids
Components
Examples
Fatty acid
Glycerol
Components of
a triglyceride
Laura Coronado
Bio 10
Chapter 3
Fats triglycerides;
Steroids
testosterone,
estrogen
Figure UN3-2b
Proteins
Functions
Components
Examples
Amino
group
Enzymes, structure,
storage, contraction,
transport, and others
Carboxyl
group
Lactase
an enzyme,
hemoglobin
a transport protein
Side
group
Amino acid
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2c
Nucleic acids
Functions
Components
Examples
Phosphate
Base
Information
storage
DNA, RNA
Sugar
Nucleotide
Laura Coronado
Bio 10
Chapter 3
Figure UN3-2d
Base
Phosphate
group
Sugar
DNA
double helix
DNA strand
Laura Coronado
DNA nucleotide
Bio 10
Chapter 3
Figure UN3-4